Medical technology in recent times has witnessed advent of numerous medical devices and microscopy techniques. A lot of these microscopy techniques are used for imaging microscopic specimens or samples for analyzing one or more characteristics of the sample, or more precisely for determining one or more characteristics of a component, for example, red blood cell (RBC), in the sample, for example, blood sample. Examples of characteristics of the component, say RBC, that may be determined may include a volumetric measurement of the RBC, a morphological study of the RBC, and so on and so forth. In general for any imaging dependent analysis, an ‘in-focus’ image or output from the imaging device is essential for carrying out specific and detailed analysis of the component of the sample. Furthermore, when the component of the sample is a non-spherical entity an orientation of the non-spherical entity with respect to the imaging device, i.e., with respect to an imaging direction, is also essential, for example, an image of the RBC standing on its side is an undesired orientation as in such orientation only sides of RBC are visible. However, with respect to the imaging direction, an image of the RBC oriented such that a full face or one side of the disc shape is visible is a desired orientation as in such orientation images will reveal lot more information which is essential for volumetric or morphological study of the RBC.
For example, a non-spherical biological entity, hereinafter also referred to as the entity, carried in a sample may be studied or inspected by detecting and analyzing interference patterns formed in interferometric microscopy, for example, digital holographic microscopy (DHM). However, throughput of an DHM device or any other imaging device, i.e., rate of number of images or interference patterns provided by the device, is highly dependent on providing the sample to a field of view, hereinafter the FOV, of the imaging device, as the sample should be provided with in depth of field at a focus of the device to obtain ‘in-focus’ or sharp images or interference patterns as output of the imaging device. Providing the entity in the sample as flowing in a flow cell, for example, similar to the way a sample is provided in flow cytometry, is an efficient way of providing the sample to the imaging device. It has several advantages, for example, it is easier to maintain the entity of the sample, for example, RBCs in the blood, in their native morphology in a fluid flow as compared to placing the entity on a slide. Furthermore, by providing the sample in a flow, the sample, and thus the entities in the sample, may be provided continuously for a time period of imaging and thus a larger amount of sample, i.e., a larger number of the entities, may be imaged which is beneficial for statistical means as compared to scanning or imaging a smaller amount of the sample.
However, providing the sample as flowing in a flow cell has also certain disadvantages. One disadvantage is focusing of the sample in the flow cell. The entities in the sample, for example, RBCs in a diluted or whole blood sample, flowing through the flow cell migrate to different sections of the flow cell and are not arranged in a desired region of the flow cell. Some of the entities while flowing in the flow cell migrate to the walls of the flow cell and contact between the entities with the wall results into surface adhesion of the entities on the flow cell walls, or entities start disintegrating to form debris. Furthermore, since the entities flow to different sections of the flow cell, some of the entities of the sample in the flow cell may be either completely out of the FOV or may be in the FOV but out of focus. The entities of the sample that are completely out of the FOV are not represented in the image of the interference pattern. The entities of the sample that are in the FOV but not in focus are imaged but parts or segments of the image or the interference pattern that represent such entities lack sharpness, i.e., are out of focus or to say that the sharpness of segments of the interference pattern or the image representing such entities are either low or not of acceptable quality or blurred.
Such entities flowing as part of the sample in the flow cell or flow channel may be brought in focus by readjusting the focus of the interferometric microscopic device or the imaging device, but the entities of the flowing samples are dynamic so there is no time to adjust the focus of the imaging device. Another approach may be to provide the sample in such a way in the flow cell that the sample flows within a desired region of the flow cell, and then the imaging device can be statically focused at the desired region with the depth of field of the imaging device aligned with the desired region and subsequently in-focus imaging of the entities of the sample may be achieved. However, it is a challenge to control the flow of sample in such flow cells, more particularly to control the entities of the sample in the flow cell, so that the samples, or the entities of the sample, are positioned or focused in a desired region of the flow cell. Furthermore, the non-spherical biological entities are also required to be oriented in a desired orientation in the desired region. Thus, the need is to focus and to orient one or more entities in the desired region, in short there is a need of aligning the non-spherical biological entity in the desired region.